Flow control valves have been used for a significant period of time in water flow and other fluid flow systems. One application in which the valve of the present invention and its competitors is useful is in heating and air conditioning systems wherein water is heated or chilled by a central heater/chiller, and then circulated in a closed loop throughout a network of rooms to heat or cool the network of rooms. For example, this device is well suited for use in a school or office building that has many rooms heated by the same recirculating water heating and/or cooling system.
A typical recirculating heating and/or cooling system comprises a central heat exchanger, a large pipe loop and a pump to pump water through the pipe loop. Within the loop are “branches” consisting of smaller side loop(s) through which a portion of the water can flow. Normally, a system includes a plurality of branches, as most buildings include a plurality of rooms. These branches might be sub-loops of the larger loop, wherein the sub-loops carry water to individual classrooms or offices. Within each classroom there is a remote heat exchanger that typically comprises a coil through which water flows. Air that passes over the heat exchanger is either cooled or heated, depending upon the temperature of the water flowing through the piping of the exchanger.
Either upstream or downstream from the pump there is a chiller or boiler containing a “central” heat exchanger where either heat is applied to the water flowing through the coil to heat the water, or a chilling substance such as Freon or cold water is applied to the water running through the pipe to cool the water. Once the water leaves the main heat exchanger area it is pumped to cause it to flow through the system. In each room within the building there will be a heat exchanger that is the equivalent or similar to a radiator one might have in a house. The radiator will often include an air handler mechanism to blow or pull air across the pipe so that the air can interact with the heat exchanger to be either heated or cooled thereby. The heated/cooled air is then moved by the air handler into the room for providing heat or coolness to the room.
One difficulty encountered in the operation of the above-described multi-branch closed loop systems involves the equitable distribution of heated or chilled water among the plurality of branches in the system. Achieving an equitable distribution of water greatly facilitates achieving an equitable distribution of heat or cool to the branches.
On a cold winter morning, it is likely that persons occupying all of the rooms in a multi-room building such as a school house, will wish to heat up the room for the day's activities. Rooms often need to be heated up in the morning, as the heat level is often decreased at night as an energy saving measure. Every teacher in every room will therefore usually turn on (or turn up) the heater when he/she first arrives in the room in the morning. In buildings with a closed loop water recirculation system, the heat is effectively turned up by a flow valve being opened to allow water which has recently been heated by the furnace to flow through each heat exchanger unit in the rooms where a teacher has turned the heat on or up.
If there are 30 cold rooms and all of the 30 flow control valves are opened at the same time (such as just prior to the start of the school day), the water in the closed loop system will move predominantly to the rooms nearest the central heating system (or pump) and less predominantly to the rooms furthest from the central heating system. A large amount of the hot water flowing through the system will tend to go to the closest room, while a significantly smaller amount will go to the furthest room. This leads to a situation where the rooms situated closest to the pump heat quickly to the desired temperature, while the more distant rooms that require the water to travel a further distance are relatively deprived of hot water, and therefore heat more slowly.
To overcome this problem and to create some flow equality between rooms, flow control valves are used. A flow control valve (which is often referred to as a flow limiting valve) controls the flow of water in a re-circulating system by limiting the amount of water that can flow through any of these branches at a particular time. For example, if rooms 101 through 130 all had a flow control valve, and if all of the teachers turned their valves on at the same time for all 30 rooms, a flow limiter would prevent the hot water from flowing predominately into room 101 (the closest room) because the flow of the hot water in room 101 would be limited by the flow control valve. By limiting flow, you would better balance the amount of hot water flowing into each of the 30 rooms in the hypothetical system described above.
When designing a system, one usually operates under the generally correct assumption that all the flow control valves in a re-circulation system will permit the same flow rate if the flow control valves are the same size and are configured similarly. If the flow control valves are properly chosen to have appropriate flow rates, based on both the water flow rate through the system, and the relative sizes of the rooms to be heated, the various rooms should all be able to become heated at approximately the same rate without regard to distance from the heat exchanger.
Prior art flow control valves exist. While the prior flow control valves do perform their function in a workmanlike manner, room for improvement exists. Room for improvement exists because there are certain limitations and problems that exist with existing flow control valves.
One of the problems with existing flow control valves is that they have a limited functional pressure range. If the pressure difference created by the fluid flow exceeds the pressure range supported by the valve, the valve will cease to function. Past their supported pressure range, the flow control valves effectively become fixed orifices. As a fixed orifice, a fully open valve allows an unlimited amount of water to flow through. A valve effectively becomes a fixed orifice because the metering disk of the valve is displaced at such a distance from its seat so that it fails to restrict the flow of water therethrough to any significant extent. When the displacement between the valve and its seat reaches a certain distance, the valve acts as a hollow pipe and loses its capacity to limit the flow of water therethrough to an appropriate flow level.
Another problem with currently existing flow control valves is that they require a certain amount of activation pressure to open the flow control valve to allow a fluid to flow therethrough. The need to provide this activation pressure forces the user to maintain a higher pressure within the system so that the valve will operate in its operating control range. Viewed another way, providing a valve that had a lower actuation pressure would permit a user to maintain a lower water pressure level in the system
One of the problems with this high activation pressure of current flow control valves is that it adds unnecessary costs to the system, since a larger pump often with higher energy requirements is required in the system in order to overcome this activation pressure. A lower activation pressure for the valve is desirable because it allows for the same flow output with a smaller pump, and therefore permits the user to employ a smaller, less expensive pump.
If the purchaser of a typical HVAC system, such as a school or a local government, can provide efficient heating or cooling with a smaller pump, there are many advantages. First, a smaller pump will be less expensive to purchase. Second, using a smaller pump will often reduce power usage and energy costs, thereby providing significant operating savings. Finally, the smaller pump will often lead to improved maintainability.
Reducing the size of the valve will likewise save the purchaser money. Typically, valve sizes are based upon the amount of flow that is allowed to flow through them. For example, a valve that permits only a quarter of a gallon of liquid to flow through per minute is usually smaller and less expensive than a valve that is designed to permit 100 gallons per minute to flow through it.
As such, one object of the present invention is to provide valves that possess an expanded operating range when compared to similar sized valves. For example, if you need to provide a volume flow rate of 20 gallons/minute, you would typically need a size six valve. With applicant's design, a less expensive size five valve might be sufficient to provide the desired flow rate due to the increased effective operating range of the valves of the present invention. Because larger valves and piping are also more expensive, Applicant's invention allows the use of less expensive (smaller) valves and piping to obtain the same functionality as larger and hence more expensive valves and piping of the prior art.
The reduction of valve size and greater operating range are also important for reasons relating to availability. Typically, retail stores only stock a limited range of valve sizes. A more efficient, smaller valve that is capable of operating over a broader range of flow conditions will reduce the likelihood that the technician working on a commercial or industrial heating or cooling system will be unable to find an appropriate valve in his local dealer's inventory, thereby saving shipping costs for the customer, and providing for more efficient maintenance of the system with fewer delays. Increasing the likelihood that a suitable valve will be found within a dealer's inventory will reduce the instances where the valve will need to be specially ordered. Additionally, it would help to reduce inventory requirements for the builders and repair shops since the present valve can operate over a broader range, thus reducing the need to stock a greater range of valve sizes.
One object of the present invention is to provide a flow limiter valve that is more cost-effective and efficient than known competitive values currently available on the market.
Another object of the present invention is to provide a flow limiting valve that provides a low variance in its flow rate throughout the control range of the valve.
Yet another object of the present invention is to provide a valve with an improved control pressure range, including a lower activation pressure.